A:

One of the mysteries of blood pressure is that it can rise or fall without any obvious changes in your life. As you grow older, the systolic pressure (the top number) in particular tends to increase.

We used to believe that it was only important to control the diastolic pressure (the bottom number). But we now know that both numbers are important. Today, we recommend that most people over age 50 focus on the systolic reading as a guide to controlling blood pressure.

A variety of conditions can cause sudden changes in systolic blood pressure. The most common include:

• Chronic kidney disease
• An overactive or underactive thyroid gland
• Overactive adrenal glands

Talk with your doctor about these so-called secondary causes of high blood pressure to see if you should have any more tests. He or she will probably ask for some simple blood tests to check for them.

No matter what the cause, your systolic blood pressure is too high. It should be under 140. And I’d like to see it at 130 or below.

Most drugs affect both the systolic and diastolic pressure. But some do have different effects on systolic and diastolic pressures.

Work with your doctor on a new program to lower your systolic blood pressure. This will almost certainly include eating a healthy diet loaded with vegetables, taking in less salt, keeping your weight in a healthy range, and getting more exercise.

You didn’t mention taking a thiazide diuretic, such as chlorthalidone. It makes sense to take a low-dose diuretic unless a diuretic causes problems for you.

Finally, keep in mind that blood pressure rises and falls. And it can be hard to measure your own blood pressure accurately.

Here are some tips when checking your blood pressure at home:

• Don’t drink coffee or smoke at least 30 minutes before the reading.
• Sit quietly for at least 5 minutes before the reading.
• Take two readings, at least 2 minutes between each one.